1. Field of the Invention
The present invention relates to improvements in motorized water hydrants of the type used, for example, in automated snow-making systems for supplying a controlled flow rate of water to a snow gun or the like. More particularly, it relates to an apparatus by which such hydrants may be manually operated, for example, in the event of an electric power failure, or an insufficient motor torque to break loose a frozen or otherwise seized valve stem or the like.
2. Discussion of the Prior Art
In the commonly assigned U.S. Pat. No. 4,989,830, issued on Feb. 5, 1991 in the name of H. Ronald Ratnik, there is disclosed a motorized water hydrant in which the flow of water through the hydrant is controlled by an electric motor. The hydrant disclosed in this patent is intended for use in an automated snow-making system in which it is desirable to control the flow of water to a "snow-gun" from a remote location. The water flow rate through the hydrant is controlled by rotating a valve stem mounted in a threaded bushing on the hydrant. One end of the valve stem is operatively connected to a plug which is shaped to mate with a valve seat through which water can enter the hydrant housing. Rotational movement of the valve stem is translated by the threaded bushing to a movement of the plug towards or away from the vane seat, thereby adjusting the volume of water that can flow through the valve seat in a given time. The vane stem is rotatably driven by a bi-directional D.C. electric motor having a rotatably driven motor shaft which is operatively coupled to the valve stem via a gearing arrangement of high gear ratio (e.g. 300:1). The latter serves to convert the relatively high speed, low torque output of the motor to the slow speed, high torque output required for tightly closing and thereafter opening the hydrant.
In motorized hydrants and valves of the above type, provisions are often made for manually operating the valve when electric power to the motor fails. In some motor-controlled valves, provision is made for accessing the motor shaft directly so that the shaft may be gripped and rotated by a wrench or the like; in other motor-controlled valves, provision is made for entering the gear train at some level of reduction in order to manually rotate one of the gears. The former approach is disadvantageous when a high reduction gear train is used in combination with the motor because the operator must provide an excessive number of turns, say, 300 turns, to rotate the valve stem one revolution (as in the hydrant discussed above). The latter approach is disadvantageous in that it usually results in a complicated mechanism for rotating the gears; moreover,this approach is particularly difficult to accomplish when using epicyclic reduction units.